The problem of "left-behind" children has been an important issue in contemporary China. This group's pain aroused a "moral shock" and public compassion in some public events. Two case studies are used to examine the representation of this subaltern group's pain in mass media and the public expression of compassion in cyberspace from the perspective of deliberative democracy theory. Mass media represent the pain of left-behind children through the language of agency, and they play an important role in making their pain a public issue. The public compassion aroused by subaltern pain has been an important motivation for public expression, which is structured by emotions such as sorrow, anger, satire, shame, and powerlessness. Netizens use both official and cultural discourses to express compassion. These findings are valuable because they contribute to considering the moral and emotional dimensions in the formation of the public sphere. Subalterns' pain is rarely expressed in the public sphere because of the inequality of political power, which inevitably leads to compassion fatigue.